Corrugated tube



M. KNAB CORRUGATED TUBE Dec. 4, 1934.

Original Filed April 2, 1930 i5 Sheets-Sheet l INVENTOR. BY W a r ATTORNEYS.

M. KNAB CORRUGATED TUBE Original Filed April 2, 1950 3 Sheets-Sheet 2 INVENTOR.

BY M Krfl.

A TTORNEYS.

. 4, 1934. KNAB CORRUGATED TUBE Original Filed April 2; 1930 3 Sheets-Sheet 3 BYW KVQ ATTORNEYS.

45 This is due to the fact that the material is Patented Dec. 4, 1934 um'rao STATES 1,983,469 L coaauaa'mn TUBE Max Email, New York, N. Exacdgnor to Sm e Specialties 00,, North Adams, Masa, a corporation of Massachusetts Original application April 2, 1930, Serial No.

Divided and this application October 29,1931, Serial No. 571,905

11 Claims, (01. 175-315) My invention relates to' the manufacture of corrugated tubes and more particularly of thin. walled tubes provided with corrugations, and embraces such tubes and novel means and processes of making same.

The present application is a division of my copending application Ser. No. 441,128, filed April 2,1930.

Qne special application of my' invention is that 1 to the manufacture of corrugated tubes of film forming metal, as aluminum, to be used as anodes for electrolytic condensers and similar devices, and I shall describe myinvention in connection with the manufacture of such tubes. 4 The dielectric capacity of a condenser of the electrolytic type is directly proportional to the' area of the anode. It is evidently of great advantage if a large anode area can be combined with a small volume, and therefore, it has been 20, propased in the copending application of Desmond Sprague and R. U. Clark, -Ser. No. 416,939, filed December 27, 1929, to use for anode a thin walled tube of film forming metal having corrugations in the form of. a helical screw thread. Such an anode in addition of combining a large area with a sniall volume, has the advantage of a strong and rigid structure, relatively small ratio of edges to surface, can be constructed from} a single piece .of metal, and has other advantages fully described in the above referred to application. v

When endeavoring to. manufacture anodes of the type referred to by various methods suggesting themselves, great dimculties have been.en-

countered. For instance, by inserting a threaded arbor in the tube and exerting pressure simultaneously on the full length of the tube, it has been found that the aluminum wouldbreak as the depth of the corrugation exceeded a.-certain 4 limit. For instance, in a tube having a diam- ,eter of 1 /4", a length of 6", a wall thickness of .020" and about 3% thread-per inch, difficulty is encountered in case the depth of the corrugation is to exceed 1 stretched in such operation and above a certain limit determined bythe tensile strength of the aluminum, the material will break. 'But even if the depth of the corrugation is kept below the limit of actual rupture of the material, deformation of the tube. will prevent the wall to be 'uni-' form in thickness and in strength.

To obtain satisfactory results, I have found it necessary to form the corrugations progressively, so as to enable the'excess material required for the corrugations to be freely drawn from the tube. I have found that in placing the tube on a rotat ing screw arbor and gradually rolling the tube around this arbor by means of a laterally moving roller, corrugationsof considerable depth could be obtained with small or no distortion of the tube. Thereby I found that to obtain satisfactory results the full required depth of the corrugations should be achieved by a simple rolling operation, and subsequent rolling operations, if any, should be restricted to the smoothing out of possible wrinkles in the corrugations without endeavoring to deepen them.

I have found, furthermore, that by using a tensioned wire, instead of a roller; still better results could be obtained and that by gradually winding such a wire around a tube when placed on a rotating screw arbor, corrugations of practically any desired depth can be obtained without distortion of the material and without change in l the wall thickness of the tube.

The advantage of using a tensioned wire as compared with a roller is due to the following facts: (0) The 'wire permits .a smaller contacting area than the roller and therefore conforms pre- 30 cisely to the shape of the thread. (1)) I'he line contact of the wire permits more freely the material to be drawn from the free end of the tube U than in case of a roller. (0') The wire wound v around the threaded portionsgof the tube forms a .35 tight grip around these portions and prevents their deformation during the further threading of the tube.

It should be well-understood that my process.

of corrugation is basically different from any 99 known method of spinning or like process previously used for the corrugation of metal tubes. In these methods the metal is stretched, whereas in my process the material is allowed to freely flow and twist around the arbor, whereby the total surface of the tube as well as the tube thickness is the same before and after corrugation. While'with the wire threading" process, as above outlined, I have found that corrugations of any desired depthv could be obtained, there are no physical limitations determining the pitch of the thread, and therefore, to form tubes of very close corrugations, I have found it desirable to subject tubes corrugated by either one of my above illustrated processes, to a novel compressing method by means of which the corrugations can be closed up to any desired pitch. It should be understood that my compressing process is independent of the type of corrugations incorporated in the tube to be collapsed as well as of the proc- 11o ess by which the corrugations have been effected. In this compressing process, I employ a device including a compressing fixture and spacing means to limit the compression of the corrugations to a predetermined and uniform limit, which in the case of anodes for electrolytic condensers is determined by the clearance required for the 'free circulation of the electrolyte between the corrugations-both on the inside and the outside.

I have also found that it is of advantage to subject the corrugated tube after its corrugation but before its compression to a rolling process placed on a mandrel and the corrugation formed on the tube by progressive pressing or rolling operation.

A further object of my invention is to provide a method of corrugation whereby a screw arbor is rotated and the tube material is caused to freely flow in the threads of the arbor.

, A further object of my invention is to provide a method of corrugation whereby the total surface area of the tube is the same before and.

after corrugation and the wall thickness of the tube remains unchanged.

A further object of my invention is to provide a method of corrugating a tube-on a rotatin screw arbor by forming the tube to the shape ofthe arbor by the means of a tensioned wire progressively wound around the tube.

A further object of my invention is to smoothen out the corrugations formed as above set forth, by a subsequent and preferably correlated rolling operation.

A further object of my invention is to compress the corrugated tube by a pressure operated compressing device, whereby spacing means are provided to limit both the outside and inside closing-up of the corrugations to a desired and fixed dimension.

Further objects of my invention will appear as the specification progresses. I

Referring now to the drawings Figure 145 a side elevation showing a tube to which my invention is to be applied. J

Fig. 2 is atop view of Fig. 1. V

Fig. 3 is a side elevation showing the tube of Fig. 1 after it has been corrugated according to a preferred method of my invention.

Fig. 4 is a side elevation of a tube as shown in Fig. 3 after such a tube has been subjected to a compressing process forming part of my invention.

Fig. 5 is a side view of a tube in the process of corrugation, with the corrugating means schematically illustrated. Y

Fig. dis a side view showing. a tube in the proces of smoothing, subsequent to its corrugation,

also showing' the smoothing roller arrangement.

Fig. '1 is a perspective view of the holding head for the screw arbor.

t Fig. 8 is a fractional side view showing the conical end of the screw arbor. Fig. 9 is a top view of the compression device, partly in section and with parts broken away,

with a corrugated tube therein prior to itscompression.

Fig.4!) is a top view of the compression device with a tube after it has been compressed. Fig. 11 is a fractional perspective view showing the left hand end of the compression device in its closed position.

Fig. 12 is a perspective view of a spacer plate of the compression device.

A- thin walled aluminum tube 10 (Fig. 1) is' open at its lower end and is provided on the other end with a conical head 11 having two locating holes 12-12. The head 11 extends in a tapered stem 13 provided with a beveled se'c- .35 provided with a threaded portion 39, a straight portion 40 and a conical head 37. The conical head is also provided with a bit or pin 36 to fit in the center bore 15a of the tube, and with two locating holes 38-38 brought in juxtaposition with the holes 12-12 of the tube when the latter is slipped over the arbor.

The straight end 40of the tube is provided with parallel flats 41-41 and a center bore 34.

The arbor 35 is placed on a lathe or similar device, whichby proper gripping of the arbor permits rotation thereof at any desired speed. For the proper securing of the arbor there is provided on the left side a head 20 comprising a conical recess 27, locating pins 28-28 and a clearance bore 25 for the stem 13 of the tube. Wheninserting the arbor 35 and tube 10 in the head 20, the pins 28-28 project in the holes 12-12 of the tube and the holes 38-38 of the arbor, tying the arbor, tube and head together and thus preventing their relative displacement when the arbor is rotated.

On its other end the arboris held by a laterally movable center 30 which when moved toward the arbor engages its center bore 34.

A wire 45, preferablyof high grade steel, is

: anchored in the head 20 and guidedin helical lead grooves 23 of the head 20 towards the tube 1 0. The end of the head 20 is cut away at 24 permitting'smooth transition of the wire from the head to the tube.

- From the 'head 20 the wire 45 is led over a pulley 46 and is properly tensioned by the combination of aspring 49 and a weight 48, as more fully explained hereafter. As the head 20 is rotated manually or preferably by motor power, the tube '10 and arbor 35 are rotating therewith and the wire is gradually wound around the tube and forces the latter to assume the corrugations determined by the thread of the arbor (as shown in Fig. 5 to the left of the line X-X) whereby on the threaded portion of the tube the wire forms a tightly gripping helix lying in the root spiral of the thread. I

It should be well understood that the wire is of suflicient length to be wound around the whole length of the tube and at the same time to permit location of the pulley 46 and of the tensioning means at any convenient distance from the arbor. I have found in practice that it is advantageous not to place right from the start the full tension on the wire, but preferably 'to increase gradually and uniformly the tension of the wire from zero to 50- sequent rolling operation.

,its ultimate value during the forming of the first thread.

For this purpose, I connect the free end of the wire with a rod 51 carrying a plate 50. On top of the plate and placed within a spring cylinder 47 is a coil spring 49 which is gradually compressed as the wire winds around the tube 10 and the plate 50 thus lifted.

The spring cylinder 47 carries at its lower end the weight 48, which rests on a suitable base when the threading is started. During the winding of the first thread the spring 49 is compressed to the value corresponding to the weight 48 and the weight now lifted so that in the further threading operation, the wire is subjected to a. fixed tension corresponding to the weight 48.

It should be noted that as the threading progressesthe-excess material required for the corrugations is drawn from the free end of the tube. This results in a corresponding shrinkage of the total length of the tube whereby, however, the metal is not stretched and the total area of the tube and the thickness of the tube remains unchanged.

It should alsobe noted that in my method of corrugation, the metal as it is caused to flow to fill outthe threads of the arbor, is also subjected to a torsion or twisting action.

The twisting effect on the tube can be observed from Figs. 1 and 3, which indicate that a line -w.a-shown in dotted lines-drawn parallel to the axis on the tube 10 before corrugation (see Fig. 1), assumes through the process of corrugation the angular position shown in Fig. 3, as line a a. For instance, in the case of a tube having a diameter of 1 /8", a length of 10" and a wall thickness of .015", corrugated with a thread having a pitch of 3 /2 threads per inch and depth, this twisting amounts to about three-quarters of a turn for the full length of the tube.

It should also be notedthat in my corrugating method the required depth of the corrugation should be obtained by a single rather than a plurality of threading operations, as once the tube is corrugated free flow of; the material will no more take place.

As during the wire threading process, a slight I amount of wrinkling of the tube takes place (as shown in an ,exaggerated mannerin Fig. 5), I prefer to smoothen out these wrinkles by a sub- This operation, I prefen'to correlate with the wire-threadingprocess and for this purpose, I

on atpin56 carried by a sti provide a roller 55 of a shape conforming .with the threads of the arbor and rotatably supported p57. A The roller 55 is brought in engagement with the tube when rotation of the head 20 is reversed to unwind the wire 45' from the tube. The roller stirrup 5'7 has an extension 58 inserted in a movable' pivot 59 which is carried by the lathe=carriage in a lateral drection and at a rate corresponding to the rotation of the arbor. The pressure exerted by this roller is suitably adjusted and as shown in Fig. 6 the roller follows the-unwinding wire whereby preferably a lag of one or two threads is provided between the wire and the roller. It should be also understood that sufllcient play is provided in th'e roller support to permit free alinement of the roller 55 with the corrugations of the tube..

After the; tube has been threaded and rolled; it

' g is removedjfrom the lathe and unscrewed from the arbon, manually or by motor driven means.

3'sh0ws the tube 104' after, the threading androllingoperation.

second roller preferably of slightly different shape 3* may, if necessary, be employed for the smoothing out of thecorrugations. 'However, it should be noted that the full depth of the corrugation is to be obtained with the first roller and the function of the "subsequent roller, as stated, is only the smoothing out of the corrugations.

Taking up now the compression device above referred to, this comprises a two-part base block 6565 (Fig. 11), hingedly connected at 80, and provided with a. hook 81 to hold the two parts together during compression. The respective parts 65-65 of the base are provided with recesses and cavities which inthe closed condition of the base form a conical depression 66, and a connecting hole 67 to receive the head 12 and 0 the stem 13 of the tube. Two pairs of guide rods 69' 69 and "69' 69' are anchored in the'upper block 65 and lower block 65 of the base respectively, in corresponding holes 68. The upper guide rods 69-69 carry a set of loosely mounted spacing plates 70 of unif orm thickness and corresponding in number to the corrugation of the tube to be compressedahd are provided with corresponding holes 71--'71' (see left side-of Figs. 9 and 12) which are spaced by springs 72 at a dis- 0 tance corresponding to the pitch of the corrugated tube 10a. The forming plates 70 are pro-. vided with semi-circular openings 79 which correspond to the smallest diameter of the cormgated tube. a

In a similar way the lowerguide rods 69'69', garry a set of spacing plates 70' (see right side of To insert a tube for its compression, the base blocks are unhooked and the upper base block 65 swung upwardly. The tube is now inserted in the lower baseblock- 65' so that its conical head 12 comes to rest in the lower half of the corresponding recess 66 with its stem 13 resting in the lower,half of thehole 67. At the same time the threaded portion 39 of the tube comes to rest between and on the lower spacer plates 70' whereby the lower half of each corrugation lies between two spacing plates 70 and rests with its portions of smallest diameter in the apertures 79 of the plates 70. The base is closed, by swinging its upper part 65 into the position shown in Fig.,11, and in so doing the upper spacing plates 70 as shown on the left side ofFig. Qengage the upper half of the tube 10 a in asimilar way as previously described in connection with the lower spacing plates 70' in reference to the lower half of the tube. "The'base blocks are then lockedtogether by means of the hook 81.. a

, An end-block 76 provided with four holes 77 146 registering with the guide rods .69 and 69' is slipped over the end of the guide rods; the compression device is then placed in a suitable press and an endwisepressure applied to the block 76. This causes the block 76 to slide on the guide rods '89 and 89' toward the base blocks 85 85 thereby compressing by means of the spacer'plates 70 and-70', the corrugations a; the tube so that the latter assumes the shape as shown as 10b in Figs. and 10. I 150 iln case I desire to compress a tube to avery smklt'pitch and prevent the possibility of the threads closing up inside of the tube, I have found it advantageous to provide spacing means also for the inside of-the tube. For example, I insert in the tube a resilient helix 73 attached to a plug '74 (as shown in Fig.9). The coils of the helix 73normally assume a spacing which corresponds to the corrugations of the non-compressed tube 10a and.permit the helix to be easily screwed in the tube. Iprefer also to insert in the tube loaa mandrel '75 having a diameter slightly less than the smallest inside diameter of the tube, for proper location of the helix 73.

It should be well understood that in'this casein compressing the tube 104:, pressure is exerted both on the end-block 76 as well as the helix plug '74, so that the two move in unison; no pressure however is exerted on the mandrel '15.

It should be also understood that the helix 73,

after it has been compressed with the tube, can

be easily unscrewed from the latter.

As an example of illustration, if an aluminum tube of about 10" length, 1% outside diameter and .015" wall thickness is corrugated by my wire threading process so as to have approximately twenty-two corrugations'of a. depth of the tube in this process will be reduced to a length of approximately 6%", if I now subject such a corrugated tube to my compression process using .040" thick spacer plate and a helix of about the same thickness, I obtain as final product a corrugated tube only'about 2%? long with corrugations having substantially rectangular profiles.

While, Ihave described my invention in connection with the manufacture of helical corrugated tubes, made of hollow aluminum cylinders and used for anodes of electrolytic condensers,

40 it should be well understood that my invention has a wide scope of application and is not limited thereto. It can be applied tovariously shaped tubes made of different metals and the individual steps here described can be used individually or combined, without departure from the scope" of my invention. Therefore, I do not wish to belimited to'the specific processes and specific construction shown and described above, but wish the appended claims to be construed as broadly as permissible in view of the prior art.

What I now claim as new and desire to secure by Letters Patent is: l

1. As a new and useful article of manufacture, a corrugated aluminum tube, the wall of which is of substantially uniform thickness throughout 1 and having corrugations, the depth of which ape proximates one-half of the radius of the tube.

2. As a new and useful article of manufacture, an aluminum tube characterized by helical corrugations, the wall of the tube being of substantially uniform thickness throughout and the depth of the corrugations being considerably, in excess of one eighth of an inch.-

3. As a new and useful artcle of manufacture, an aluminum tube having corrugations the depth of which approximates one-half of the radius of the tube. A, 4. As a new and useful article of manufacture,

an aluminum tube provided with corrugations having substantiallvparallel faces and having substantially uniform thickness throughout, whereby the clearance between the wallsof the corrugation on the inside and the outside of the tube is'substantially the same, and the depth of the corrugation approximates one-half of the radius of the tube. 1

5. As a new and useful article of manufacture,- 'a corrugatedaluminum tube having more than five corrugations per linear inch, said corrugations having a depth which approximates onehalf of the radius of the tube.

6. As a new and useful article of manufacture, an aluminum tube having corrugations the depth of which is materially in excess of one-eighth of one inch, the'wall'of said tube beingof substantially uniform thickness throughout said corrugations.

7. As a new and useful article of manufacture,

*a corrugated aluminum tube the wall of which is uniform and of substantially the same thickness .-as before corrugation and having corrugations the depths of which are materially in excess of one-eighth of an inch. I 8. As a new and useful article of manufacture, an aluminum tube characterized by helical corrugations, the wall of which is of substantially uniform thickness throughout-said corrugations having fiat and substantially parallel faces and arlepth approximating one-half of the radius of the tube. Y

9. As a new and useful article of manufacture,-.115 ,a corrugated aluminum tube characterized by closely spaced fiat corrugations having substantially parallel faces, the depth of the corrugations approximating one-half of the radius of thetube.

10: As a new and useful article ,of manufac-. ture, a corrugated aluminum tube, the wall of which is of substantially uniform thickness throughout and comprises more than five corrugations per linear inch, the depth of the corrugations being materially in excess of oneeighth of one inch.

11. As a new and useful article of manufacture,'a thin walled corrugated aluminum" tube,

the wall of which is of substantially uniform thickness throughout and comprises more than five corrugations per linear inch,'the depth of the corrugation being materially in excess of one-eighth of one inch. I f KNAB- 

